var flag = true;
function checkInterest(){
        var interest = document.getElementsByName('interest');
        for(i=0;i<interest.length;i++){
            interest[i].checked = flag;
        }
        if(flag){
            document.getElementById('btn1' ).value= "全不选";
        }else{
            document.getElementById('btn1' ).value= "全选";
        }   
        flag = !flag;    // 开关变量

}
function checkInterest1(){
        var interest = document.getElementsByName('interest');
        for(i=0;i<interest.length;i++){
            interest[i].checked =! interest[i].checked;
        }

}